Percussion drill



Patented Dec; 3, 1940 UNITED STATES- PATENT o FICe Carl Hiimen, Hamburg, Germany Application June 21, 1939, Serial No. 280,230

In Germany April 24, 1939 2 Claims.

This invention relates to compound percussion drills, that is to say, drills which can be arranged to operate either *with a percussion or with a,

rotary action, or with a combined rotary and 5 percussion action.

,One object of the invention is to improve the l the construction of such drills to produce a cheaper and more robust instrument. i

A further object of the invention is to provide a compound drill which can easily and simply be switched over from the percussion action to it the rotary action and vice versa.

These and other objects will best be understood from the following description, in which-one form of drill in accordance with the invention is described by way of example and with reference 20 to the accompanying drawing, in which- Figure l is a longitudinal section through the drill,

'Figure 2 is a view of the clutch immediately after a blow has been delivered;

25 Figure 3 is a similar view just before a blow is delivered; and

Figure 4 is a plan of the brake mechanism used to convert the tool into a pure impact drill.

The'drill shown in the example is driven by 30 an electric motor. All the driving, members are housed in the casing consisting of two parts I and 2, the upper'part I carrying the handle 3 by which the drill is held. Inthe upperpart I of ,the casing magnetic poles 4 are arranged, be- 35 tweenwhich a cylindrical armature 5 revolves. The armature 5 is carried on an inner cylindrical .casing 6 which is rotatably mounted, by means of ball bearings ,Iyon ,the inner casing 2 which;

projects upwardly into the outer casing I.

40 The inner armature casing 6 carries 'a cover 8 which is secured to the bush! which is in turn fixed to the driving shaft III, which is journaled at its upper end in th'top of the upper part I of the casing. The driving shaft I0 carries at its 45 lower end' a hammer head 'II and the driving member I2 of a'dog clutch, this member being the casing part 2. The upper end of the bit 5; holder l5"""earries an impact head l6 which is positioned opposite the hammerhead II. The bit holder I4 is urged downwards by means of a spring I'I, whilst another spring I8 presses downwards on the driving member I2 of the dog clutch. In order to make it possible to adjust the force of the impacts, an adjusting device I9 is provided in the head of the casing part I, which I enables the compression of the spring I8 to be adjusted, and hence the force of the impacts, by moving the collar 20. The device I9 can be held 1 firmly in any desired position by means of the .spring clamp 2|.

To avoid the possibility of the bit 22. being flung out of the holder M as a result of an impact froni the drill occurring before the tool has been correctly positioned against the workpiece, an occurrence which might lead to injury of the operator, a spring safety catch 23 is provided on the holder I4, which engages a collar 24 on the bit 22, when the tool is in operation. The spring action of this catch also prevents the bit working loose in the holder when the tool is in operation.

A depth indicating device25 is arranged on the lower part of the drill, which can be moved up and down and secured in any position. It may 25 enclose the catch 23, so that it will not interfere with it. This enables a workman to determine before hand the depth of the hole being drilled and prevents this depth being exceeded. This is particularly useful when dowels or pegs are'to be subsequently inserted into the holes and are of a fixed size. In order toincrease th number of blows delivered in unit time, a br e is provided to impede therotation of the bit-holder and comprises two wedge shaped brake blocks 26 which engage corresponding conical surfaces on the brake rim I3. Thebrake blocks 26 are pressed against the brake rim I3 by means of springs 21 which are actuated by intermediate members 28 which in turn are pressed inwards by means of the conical surface 29 on the sleeve '32. By applying the brake to a sufficient extent the rotation of the bit can be entirely stopped so that the tool works purely as a er'cussion drill.

It is also possible to make the tool function purely as a rotary drill, even when turning in the same direction as when operating as a combined rotary and impact drill. This is done by means of the sliding pins 30', which are operated 59 so as to enter the groove in the driving member I2 and thus prevents the dog clutch from disengaging, so that no blows can be delivered. The pins 30 are spring biased towards their inoperative positions and are brought into operation by '55 -tively unskilled workmen.

means of the conical surface 3| on the sleeve 32. When this sleeve is in its normal position both the pins 30 and the brake blocks 26 are out of action. When the sleeve is moved upwards (towards the handle) the pins 30 are brought into operation, and when it is pushed downwards the brake is brought into operation. The fact that a single control member performed both these functions is a great advantage, as it automatically ensures that the two devices cannot be brought into operation simultaneously, a matter of im-. portance as the tools are usually used by relaalso prevents damage to the essential parts of the machine by incorrect use.

In order to avoid having to replace the whole of both clutch members when the dogs of the,

clutch become worn or damaged, the dogs are pressed on to their respective members [2 and I3 and secured by pins or dowels as shown in Figure 1.

The operation of the drill is as follows:

When the drill is switched on, the armature 5 rotates, driving the shaft l0 and clutch member l2 with it. As the bit 22,initially encounters no resistance, it is rotated through the clutch. If the tool is now brought against a piece of brick- Work, the frictional resistance may still remain fairly small to start with if the material is soft and in this case the drill continues to operate as. a rotary one. If the bit then encounters hard material, the corresponding frictional resistance to .rotation will increase. The bit holder I4 is then prevented from turning, so that the clutch member [3 is held fast. This causes the clutch member l2 to lift against the force of the spring l8 and to disengage. As the clutch re-engages the hammer H delivers a blow on the head l6, so that the projecting piece of material at the bottom of the hole, which waspreventing rotation of the bit, is broken away. The bit can then continue to turn until it encounters the next obstacle in the hole.

If a hole is to be drilled in soft material, the sleeve 32 can be moved upwards (as viewed in Figure 1) so that the clutch is prevented from disengaging by means of the pins 30, so that no blows can be delivered.

If, on the other hand, a hole is to be drilled in a hard material the brake blocks 26 are urged against the brake rim by means of the sleeve 32, which is screwed downwards as viewed in Figure 1, so that rotation of the bit 22 is prevented and the clutch is continually engaged and disengaged so that continual blows are delivered. The operator works with one hand onthe handle 3 and This arrangement claims.

I claim:

1. A compound rotary and percussion drill, comprising a hollow cylindrical armature, a driving shaft connected to said armature, a bitholder co-axial with said driving shaft, an overrimning clutch comprising a driven member and a driving member, said driven vmember being connected to said bit holder, said driving member being mounted on said driving shaft, a spring compressed by said driving member, upon relative angular movement of said driving and driven members, said clutch being disengaged against the action of said spring upon relative angular movement between said driving shaft and said bit holder, a hammer operative upon a re-engagement of said clutch and when said spring is extended again to deliver a blow to said bit holder, locking means for locking said clutch against disengagement, braking means for locking said bit holder against rotation, and control means for operating said locking means and said braking means separately and to prevent them from operating together.

2. A compound rotary and percussion drill,

comprising a driving shaft, a bit holder co-axial' with said driving shaft, a clutch connecting said driving shaft with said bit holder and including a spring; said clutch being disengaged against the action of said spring upon relative angular movement between said driving shaft and said bit holder, means operable upon a re-engagement of said clutch to deliver a blow to said bit holder, locking means for locking said clutch against disengagement, braking means for locking said bit holderagainst rotation, and control means for operating said locking means and said braking means to operate said locking means and said braking means separately and to prevent them from operating together, and comprising an axially movable sleeve having two inner conical surfaces, one of said surfaces being adapted to engage means operating.

said locking means, the other one of said surfaces being adapted to'engage means operating said braking means.

- CARL nii EN. 

